1. Field of the Invention
The present invention relates to a method for manufacturing a fringe field switching mode liquid crystal display device, and in particular to an improved method for manufacturing a fringe field switching mode liquid crystal display device which can reduce steps of the manufacturing process.
2. Description of the Background Art
A fringe field switching mode liquid crystal display device (high aperture ratio and transmissibility liquid crystal display device) has been suggested to improve a low aperture ratio and transmissibility of a general IPS mode liquid crystal display device, and filed in Korea under Application No. 98-9243.
In the fringe field switching mode liquid crystal display device, a counter electrode and a pixel electrode consist of a transparent conductive material. An interval between the counter electrode and the pixel electrode is narrower than an interval between upper and lower substrates. A fringe field is formed at the upper portions of the counter electrode and the pixel electrode.
A conventional method for manufacturing a fringe field switching mode liquid crystal display device will now be described with reference to FIG. 1.
As illustrated in FIG. 1, an indium tin oxide (ITO) layer is formed at the upper portion of a lower transparent insulating substrate 1 according to a sputtering method, by using Ar gas, O.sub.2 gas and ITO gas. The ITO layer is patterned to have a comb or plate shape, thereby forming a counter electrode 2 (first mask process).
Thereafter, an opaque metal film is formed according to the sputtering method at the upper portion of the lower substrate 1 where the counter electrode 2 has been formed. A gate bus line 3 and a common electrode line (not shown) are formed by patterning a predetermined portion of the opaque metal film (second mask process).
A gate insulating film 4, an amorphous silicon layer 5 for a channel and a doped amorphous silicon layer 6 are stacked at the upper portion of the transparent insulating film 1 where the gate bus line 3 has been formed, and patterned to have a thin film transistor shape (third mask process).
An ITO layer is deposited over the resultant structure according to the sputtering method, and patterned on the counter electrode 2 to have a comb shape, thereby forming a pixel electrode 7 (fourth mask process).
A pad is opened by removing the gate insulating film on a gate pad unit (fifth mask process).
Thereafter, an opaque metal film is deposited over the resultant structure according to the sputtering method. A source electrode 8a , a drain electrode 8b and a data bus line (not shown) are formed by etching a predetermined portion of the opaque metal film (sixth mask process). The exposed doped amorphous silicon layer 7 is removed according to a publicly known method. Here, the opened gate pad unit and a metal film for a data bus line are contacted.
However, as described above, the conventional method requires six mask processes for forming a lower substrate structure of the fringe field switching mode liquid crystal display device.
Here, the mask process is a photography including a resist spreading process, an exposure process, a developing process, an etching process and a resist removing process. Accordingly, it takes a long time to carry out one mask process.
As a result, a manufacturing time and cost of the fringe field switching mode liquid crystal display device are remarkably increased, and thus a yield thereof is reduced.